Translation of modulated electric current into a series of impulses



y 2, 1942. M. D. MO ARLANE I -2,z83,157

TRANSLATION OF MODULATED ELECTRIC CURRENT INTO A SERIES OF IMPULSES Original Filed J1me s, 1926 INVENTOR.

Patented May 12, 1942 U T D STATES! R ram OFFICE- TRANSLATION OF MODULATED ELECTRIC CURRENT INTO A SE8 F ULSES Maynard D. McFarlane, Hollywood, Calif.

Original application June 3, 1926, Serial No.

113,432, new Patent No. 2,070,913, dated February 16, 1937.

Divided and this application August 21, 1936, Serial No. 9?,203. In Great Britain April 1, 1926 25 Claims;

This invention relates to the conversion of a modulated electric current into a series of impulses; and this application is a divisionof my application Serial No. 113,432 flied June 3, 1926, now patent No. 2,070,913, issued Feb. 16, 1937.

(Cl. re-7.1)

' modulated electric current is applicable to a wide,

pulses in therform of a message as transmitted in standard telegraphic practice;

In systems of telephotography. it is generally necessary to form a reproduction of the representation to be transmitted and such systems have been proposed in which light transmitted through a negative has been caused tomodulate the current flow man electrical circuit, other apparatus being operated by these modulated fignals to re-constitute the original representa- Other and comparatively complicated systems have been proposed according to which electri-' photography described in our prior British Patent No. 197,402 according to which an intermediate record-of the original was made-in the form of a perforated tape preferably employing the 5-unit' or Baudot code. While this method of transmission obtains very satisfactory results the extra apparatus required to make the inter? mediate record at either or both ends of the transmission line is not essential where a private which a particular example is hereinafter given by way of illustration of the application of the -invention. Itis to be understood, however, that the utilization of said impulses derived from the variety of uses and is in no way limited to the specific application described. r

A feature of the invention is the application of a modulated electric current converted into a series of impulses, according to my invention, to the transmission of a picture or other representation of an original. This can ,be effected with or without the formation of an intermediate record. I

With the above object in view the invention may embody a method of controlling an electrical system whereby a modulated electric current is transformed into a series of impulses, said method comprising impressing upon an electric current fluctuations caused by modulations due to an exciting cause and means transforming said modulated current into a series of impulses which maybe utilized for any desired purpose.

Also, the invention may embody a method of I controlling an electrical system in which fluctuations representing variations of an original are impressed upon the electric current and the series of impulses obtained are utilized to produce a representation of said original.

Further, the invention may embody a method in which light is thrown upon a pictorial or other representation and the tones thereof interpreted by the varying amount of transmitted or reflected light, said light acting to modulate the electric current which is transformed to produce a series of impulses. v

t The invention may also include transforming the modulated current obtained by the method set forth in the preceding paragraph into a series of telegraphic impulses by the use of relay means,

The invention also contemplates a method of pictorial or other transmission, comprising employing a negative'or print of a representation to control light sensitive modulatingmeans acting to impress fluctuations corresponding to the amount of light transmitted or reflected by said negative or print upon an electrical current flowing in a circuit and transforming said modulatlng current into a series of impulses adapted to be utilized in forming a reproduction of said representation.

The invention further comprises apparatus for controlling an electrical system comprising modulating means adapted to be acted on by fluctuations desired to beregistered, said fluctuations being impressed upon said system by said modulating means and means acting to transform the resulting modulated current into a series of impulses. I

The invention further comprises apparatus as set forth in the preceding paragraphs in which said impulses are utilized to control means acting to record said variations.

The invention still further comprises apparatus for controlling an electrical system by modulating means in the form of a light sensitive element such as a photo-electric cell, and means for impressing said fluctuations upon said system and transforming the modulations into a, series of impulses.

Further features of the invention will hereinafter appear and be specifics y pointed out in the appended claims.

The accompanying drawing is a schematic diagram showing apparatus which may be used in carrying out the present invention.

In the figure, 1 represents a picture or other subject to be transmitted, mounted upon a cylinder 2, which is mounted upon a shaft 4 rotatable by a suitable gearing arranged in the gear case 5. The shaft 4 is provided with a thread, and under control of the gearing in the gear case 5, the

meals? Ila, lib, llc, a and m. For the sake of convenience, the perforating mechanism may be used for producing a tape adapted to be utilized in a standard five unit transmittingmachine.

The current flowing through the photo-electric cell is amplified by any suitable means, but pref-' erably by the use of electronic valve devices, such as 3-electrode amplifiers, and one suitable circuit is here described. The photo-electric cell is connected in the grid circuit of the electronic valve device, for instance a pair of 3-electrode tubes, as will be understood by those familiar with amplification withthese devices. The current flowing inthe circuit is a current which may be of any suitable kind as D. C. or one having a varying value of a constant characteristic'such as a pulrotation of said shaft rotates and laterally feeds the pictureacross the path of a pencil of light projected onto the surface of the picture by a suitable source of illumination arranged in the casing I; the light controlled by the characteristics of the picture or other subject I, then being reflected and falling upon the photo-electric I cell I.

Suitable opacn systems, indicated in the.dia-

gram by lenses l and 9, may be arranged to focus the light spot on the surface of the picture and to collect thelight reflected.

It has heretofore been proposed to use a photographic transparency of the original to be trans-' mitted, and to shine a beam of light through this transparency, utilizing the light transmitted by a small area to energize the photo-electric cell.

While this form of analyzing means gives satisfactory results, I prefer to use the arrangement of the apparatus illustrated, in which the picture or other subject to be transmitted is in the form of a print mounted upon a cylinder; and the light reflected from the surface thereof influences the photo-electric cell I. This arrangement pos-" sesses considerable advantage over the arrangement employing the transparency since it is not necessary to prepare a transparency for the purpose of transmitting the picture.

A further modification of the analyzing means ,(not illustrated) which may have advantages in particular circumstances, is to employ a beam of light in place of the focused pencil in the arrangements Just described, the light reflected from a point within the illuminated area being directed by a suitable lens system upon the photo-electric cell.

' As shown in the drawing, the pencil of light sating current; the latter form is convenient in that the usual transformer devices may be utilized for .voltage amplification. Current may of course be supplied from any suitable source, as for instance a direct current generator or a source of direct current used in conjunction with suitable means such as a mechanically operated commutator, a buzzer, or an oscillator tubeto transform continuous into intermittent current.

The photo-electric cell I is shown connected to v the grid of the 3-electrode amplifier tubes l4 and amplifying circuits without a grid'leak and biasing battery can be employed; for instance very satisfactory amplification has been obtained from a circuit in which neither a grid leak nor biasing battery are utilized, although in this case careful adjustment of the voltages applied to the photoelectric cell and amplifying tube or tubes is required.

It will further be understood that when a pulsating current is used, means supplying the interrupted current may be positioned in any suitable part of the circuit and not necessarily before the first amplifying tube and further it will be understood that any suitable arrangement or number of amplifying tubes may be employed;

. for instance satisfactory results have been obtained from two or three amplifying tubes arranged in parallel as well as from a number of tubes arrangedin straight cascade formation.

' It will be observed that the tubes shown in the circuit arrangement are supplied by a common lead. In the case of a pulsating current modulated by the photo-electric cell, or a series of pulsating light impulses, the amplification may of course be by any suitable means such as trans formers, resistance coupling, capacity coupling and the like.

shown.

operating windings of these relays are connected in series in the plate lead of the tubes l4 and I5. Thus the current from the batteries l'l passes through the operating windings of the relays lfle, ld, lflc, ltb and its in se-- quence andthence to the'plates of the tubes It and I5. Thus, the fluctuations of current caused by the light sensitive element I are impressed upon the grids of the amplifying tubesexerted on the tongues of said relays.

Each relay Ilia, lllb, lflc, ltd and Ida has its restraining or biasing winding connected to a source of current zl through appropriate adjustable resistances lla, lib, llc, lld and lie, in

such amanner that the biasing current to the relay Illa is controlled by the setting of the resistance lla, that of lllb by the resistance llb etcetra. The setting of the resistance lla therefore controls the current necessary in the operating winding-oi the relay lta to operate it, and similarly the operating current for the relay ltb is controlled by the resistance llb, and so on.

rendered or to the employment of a standard form of perforated tape, since even'when using.

such a tape it is possible to render 32 tones. Five tones have been found generally satisfactory for commercial use or possibly a smaller number of tones might serve the purpose required (as when transmitting a black and white drawing, signature or the like), but on the other hand a larger number of tones might be desirable when rendering the tones of a very delicately shaded subject.

It will also be realized that for ease in transmission, the standard telegraphic tape is generally suitable and convenient. An intermediate record produced need not be in the form of such a tape,'some other form of record having perhaps special value in connection with some It is found that by this arrangement of control means, the relays may be very readily set for diiferent values of operating current. It will 'beunderstood that it is impractical to permanently adjust the relays since each picture, to obtain the best results, should be analyzed into tones depending on the range of tone of the picture. For instance suppose a print is being used at l and the amount of variation in the operating c'urrentis twenty milliamperes, effected by the current ranging from fortyrtosixty milliamperes, it mightzbe possible to obtain satisfactory rendition of the tones with relays set to operate at differences of four milliamperes, i. e. to opperes. negative or print are a logarithmic function of particular method of reproductions of a representation.

. It is desired to point out that where the mechanism so far described is used to operate a perforator of standard type by which a standard perforated tape is produced, the tape may be utilized either for forming a direct reproduction of the transmitted picture or for sending signals, with which to operate a similar perforating mechanism at the receiving station to form a duplicate perforated tape; and it is of course feasible to send a picture analyzed into impulses directly to a receiving station (withoutforming the intermediate record) and use these signals to effect the reproduction of the representation transmitted.

cults is improved by the use of vibratory circuits erate at forty-four, forty-eight, etc. milliam- However, the density of the shades of a.

the light received by the film on taking the photograph, and conversely. Obviously, therefore, an arithmetical progression of increase of current would not cause the relays to operate in true- Apart from this feature, however, there is an inherent difference in the character of the pictures to be transmitted. It might also be desired to vary'the tones'of'the reproduction from those of the original; and His avery important feature that this effect is readily obtained by the adjustment of the relays, as for instance to arrange them in a series operating on currents of-forty, forty-six, fifty-one, fifty-eight and sixty milliamperes. The improved control over the tone grading of the picture transmitted is, it will be realized, a very important feature of the invention.

The tongues of the relays Illa, lllbplllc, lld

and llle are adapted to close circuits through in- Whenever standard forms of polar relays are used the operation of such relays may be improved in various ways. It is well known that the operation of such relays in telegraph cirwhichhave become standard. These standard vibratory circuits can be more or less directly applied to the circuits herein described; Alternatively the action of the relays may be improved by passing weak alternating current through one or more windings of the relay. for instance,-

through the vibrating winding thereof, or again,

weak alternating current of suitable frequency may be super-imposed in any suitable manner on the operating or biasing currents of the said relays.

Another possible method for improving the operations of the relays is to supply one or more of the windings of the relays with pulsating current, for instance, by inserting an automatic makeand-break in the biasing winding or in the common return of a bank of relays; and the speed of the make-and-break is pregera bly timed to have a definite ratio to the speed of operation of "the punching mechanism, asfor instance, by

dividual selector magnets, 01' which only one Ila is shown in the drawing. Thus current from the .source l3 flows through the'contacts of the relays and the appropriate tongues thereof to cause the selection of the code combination to be perforated in the tape. The perforating mechanism itself is shown in the above mentioned British Patents Nos. 197,402 and 195,577.

In the embodiment of the invention herein discussed, the'perforation of a standard telegraphic tape to render five tones has been described. It is understood, however, that the invention is being operated by said punching mechanism.

It is believed that the operation ofmy invention will be readily understood and further explanation is not therefore-considered necessary, but a short follows: 7 p

The current flowing ina circuit, such as a direct current or interrupted current, is modulated by suitable means acting'to render tones or variations desired to be registered and the modulated current is transformed into a series of impulses. These impulses (telegraphic or other) are used to operate suitable mechanism.

, Where in theappended claims I have referred to a picture, it is understood that reference is made to an original subject which is to be transmitted; this original subject-may be in the form not in any way limited to the number of tones of a picture, photograph, drawing. printed matsummary thereof may be stated as' produce a replica at a receiving station.

where I have referred to unit areas or elemental areas of a picture or subject to be transmitted, it is to be understood that these terms refer to the elements into which the picture or other subject is resolved for purposes of transareas into which the original subject has been resolved by the scanning means.

; Having now described my invention, I claim: 1..In a picture transmission system in which the line current transmitted to a receiving station is varied so that the variations in said line current shall correspond to the varying tone value of successive elemental small areas of a picture or the like which is to be transmitted, means for causing a pencil of light whose intensity varies with the tone value of thesuccessive small areas to produce an electric current of corresponding varying intensity, a plurality of relay devices selectively operable in accordance with the intensity of said current, and an adjustable resistive element for controlling the biasing .current for at least one of said relay devices.

2. In a picture transmission system, in which the line current transmitted to a receiving station is varied so that the variations in said line current shall correspond to the varying tone value of successive elemental small areas of a picture or the like which is to be transmitted, means for causing a pencil of light whose intensity varies with the tone value of the successive small areas to produce an electric current of corresponding varying intensity. a plurality of polarized adjustable relays selectively operable in accordance with the intensity of said current, and means for controlling the biasing current of said relays.

3. In a picture transmission system, in which the line current transmitted to a receiving station is varied so that the variations in said line current shall correspond to the varying tone value of successive elemental small areas of a picture orthe like which is to be transmitted, means for causing a pencil of light whose intensity varies with the tone value of the successive small areas to produce an electric current of corresponding varying intensity, a plurality of polarized adjustable relays selectively operable in accordance with the intensity of said current, and means for controlling the biasing current of said relays, said means including a sistances.

4. In apicture transmission system, means for causing a pencil of-light whose intensity varies with the tone value of successive elemental small areas of a picture or the like to be registered to produce electric impulses of corresponding varying intensity, a plurality of separate electric circuits adapted'to be energized at varying impulse intensities, and means for setting said electric circuits to select and render the varying intensity impulses into telegraphic impulses of substantially constant intensity and varying duration.

5. In a picture system, in which the line current transmitted to a receiving station is varied so that the variations in said line current shall correspond to the varying tone value of succesplurality of adjustable re-v .'ter,' or any other subject of which it is desired to sive elemental small areas of a icture or the like which is to be transmitted, means for causing a pencil of light to be reflected from the surface of said picture to produce an electric current of varying intensity corresponding to the tone value of successive small areas, a plurality of relay devices selectively'operable in accordance with the intensity of said current, and an adjustable resistive element for controlling the biasing current for at least one of said relay devices.

0. In the art of telautography, that step in the art which consists in causing a beam of light to be reflected from a picture which is to be transmitted and causing said reflected beam of light to produce an electric pulse of intensity corresponding to the tone value of a unit area of said picture.

7. In the art of telautography, those steps in the art which consist in causing a beam of light to be reflected from a picture which is to be transmitted, causing said reflected beam of light to produce an electric pulse of intensity correspond-e ing to the tone value of a unit area of said picture, and causing said electric pulse to directly control the line circuit.

a. In the art of telautography, those steps in the art which consist in causing a beam of light to impinge on a picture which is to be transmitted and causing light reflected from a unit area of the surface of said picture to produce an electric pulse of intensity corresponding to the tone value of said unit area.

9. In the art of telautography, means to cause a beam of light to impinge on the surface of a picture which is to be transmitted, and means for applying light reflected from a unit area of said surface at an angle other than the angle of said beam to'cause the p uction of an electric pulse of intensity corresponding to the tone value of said unit area.

10. In the art of telautography, means to illuminate successive elemental areas of the surface of a picture which is to be transmitted, and

means for producing electric pulses by light nonspecularly reflected from said elemental areas of the surface, the pulses corresponding the tone values of the elemental areas.

11. In the art r telautography, means to illuminate successive elemental areas of a picture which is to be transmitted, means to produce electric pulses by light non-specularly reflected from said elemental areas ofthe surface of said picture, the pulses corresponding to the tone values of said elemental areas, and means for amplifying said pulses to produce a signal for the production of a representation of said picture.

- 12. In a picture transmission system, means to pass successive small areas of a picture which is to be transmitted before a scanning mechanism, and means for causing non-specular reflections from the succession of unit areas to produce a succession of electric pulses of value corresponding to the tone value of said unit 'of pictures comprising: a source of light. means to establish a beam of light from said source,

' means to advance a picture relative to the beam to cause successive elemental areas thereof to influence the beam of light, means to produce an electric current by non-specular reflection from the picture, and means to select circuits corresponding to the intensity of the reflected light. 15. Apparatus pertaining to the transmission of pictures comprising: a source of light, means to establish a beam of light from said source, -means to advance a picture relative to the beam like before said cell, means to illuminate said elemental areas and to produce an electric current in said cell corresponding to the intensity of non-specular reflection of the light from said succession of elemental areas.

17. Apparatus pertaining to the transmission of pictures comprising: a photo-electric cell, means to pass elemental areas of a picture before said cell, means to illuminate said elemental areas and to produce an electric current in said cell corresponding to the intensity of non-specular reflection of the light from said succession of elemental areas, and apparatus to amplify the output of said photo-electric cell.

. 18. In a picture transmission system a scanning mechanism comprising means to illuminate a picture which is to be transmitted and means succession of electrical impulses in said photoresponsive device through the agency of light from said source reflected from said picture, the said impulses corresponding to the tonal values of successive small elemental areas of said picture.

22. In a picture transmission system wherein a succession of signals corresponding to the tonal values of a succession of elemental areas of a picture is transmitted from a sending station to a receiving station, a picture, a source of light, means to illuminate an elemental area from said source, aphoto-electric device adapted to be influenced by light reflected from said area, means to cause a relative movement between said picture and said source of light and said photo-responsive device to scan a-succession oi similar elemental areas, and circuit means controlled by the photo-electric device for the production of said transmitted signals.

23. In a picture transmission system a transmitting cylinder, an original subject which is to be transmitted mounted on said cylinder, means to rotate said cylinder, an optical system, means to scan the original subject on said cylinder with said optical system; a light sensitive element in said optical system, means to activate said light sensitive element by light reflected from said original subject on said cylinder, and means to produceunder the control of said light sensitive element signals corresponding to the tonal values of individual unit areas of said original subject.

to collect non-specularly reflected light from the surface of said picture and influence an electric circuit thereby to produce electric currents in said circuit corresponding to the tonal intensities of said elemental areas...

19. In the method of electrically transmitting pictures, those steps which comprise: illuminating a photoresponsive device by diifuse reflection from a succession of elemental areas'of a picture to be transmitted, and producing therefrom a flowing in a circuit.

21.. In a picture transmission system, an opaque picture to be transmitted, a photo-responsive device, a source oi light, and means to produce a 24. In a picture transmission system a transmitting cylinder, an original subject which is to be transmitted mounted on said cylinder, means to rotate said cylinder, an optical system, means to scan the original subject on said cylinder with said optical system; a photo-electric cell in said optical system, means to activate said photo-electric cell by light diffusely reflected from said original subject on said cylinder, and means to produce under the control of said photo-electric cell signals corresponding to the tonal values of individual unit areas of said original subject.

25. In a picture transmission system in which the line current transmitted to a receiving station is varied" so that the variations in said line current shall correspond to the varying tone value of relay devices selectively operable in accord- I ance with the intensity of said current, and adjustable means for controlling the relay selection in response to a predetermined intensity.

- MAYNARD D. McFARLANE.

picture current 

